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- Title
- DELAY SENSITIVE ROUTING FOR REAL TIME TRAFFIC OVER AD-HOC NETWORKS.
- Creator
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Darshana, Dipika, Chatterjee, Mainak, University of Central Florida
- Abstract / Description
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Wireless ad hoc network consists of inexpensive nodes that form a mobile communication network. Due to limitations of the transmission range, the nodes rely on each other to forward packets such that messages can be delivered across the network. The selection of the path along which a packet is forwarded from the source node to the destination node is done by the routing algorithm. Most commonly used routing algorithms, though effective for non-real time applications, cannot handle real-time...
Show moreWireless ad hoc network consists of inexpensive nodes that form a mobile communication network. Due to limitations of the transmission range, the nodes rely on each other to forward packets such that messages can be delivered across the network. The selection of the path along which a packet is forwarded from the source node to the destination node is done by the routing algorithm. Most commonly used routing algorithms, though effective for non-real time applications, cannot handle real-time applications that require strict delay bounds on packet delivery. In this thesis, we propose a routing protocol that ensures timely delivery of real time data packets. The idea is to route packets in such a way that irrespective of factors like traffic load and node density, the average delay remains within acceptable bounds. This is done by carefully accessing the resources available to a route before a session is admitted along that route. Each link in the route is checked for sufficient bandwidth not only for the new session to be admitted but also for the sessions that are already using that link. The new session is admitted only if the admission does not violate the delay bounds of any on-going sessions. This method of route selection coupled with per-hop link reservations allows us to provide bounds on the delay performance. Extensive simulation experiments have been conducted that demonstrate the performance of the proposed routing protocol in terms of throughput, session blocking probability, packet drop probability, average path length, and delay.
Show less - Date Issued
- 2008
- Identifier
- CFE0002355, ucf:47796
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002355
- Title
- Leader Psychology and Civil War Behavior.
- Creator
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Smith, Gary, Schafer, Mark, Kang, Kyungkook, Powell, Jonathan, Walker, Stephen, University of Central Florida
- Abstract / Description
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How do the psychological characteristics of world leaders affect civil wars? Multiple studies have investigated how the personalities and beliefs of world leaders affect foreign policy preferences and outcomes. However, this research has yet to be applied to the intrastate context, which is problematic, given the growing importance of civil wars in the conflict-studies literature. This dissertation project utilizes at-a-distance profiling methods to investigate how leaders and their...
Show moreHow do the psychological characteristics of world leaders affect civil wars? Multiple studies have investigated how the personalities and beliefs of world leaders affect foreign policy preferences and outcomes. However, this research has yet to be applied to the intrastate context, which is problematic, given the growing importance of civil wars in the conflict-studies literature. This dissertation project utilizes at-a-distance profiling methods to investigate how leaders and their psychological characteristics can affect the likelihood, severity, and duration of civil conflicts. The findings of this research provide further support for the general hypothesis that leaders can, and often do, matter when trying to explain policy outcomes. More importantly, the findings demonstrate that leaders can influence the likelihood of civil war onset, the severity of civil wars, and their duration. Additionally, this project investigates the effect that civil war severity has on the psychological characteristics of leaders. Contrary to some previous research, however, the findings here indicate that leaders' psychology may not be sensitive to civil conflict severity.
Show less - Date Issued
- 2018
- Identifier
- CFE0007375, ucf:52089
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007375
- Title
- Non-Hermitian Optics.
- Creator
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Ulhassan, Absar, Christodoulides, Demetrios, Khajavikhan, Mercedeh, Likamwa, Patrick, Kaup, David, University of Central Florida
- Abstract / Description
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From the viewpoint of quantum mechanics, a system must always be Hermitian since all its corresponding eigenvalues must be real. In contrast, the eigenvalues of open systems-unrestrained because of either decay or amplification-can be in general complex. Not so long ago, a certain class of non-Hermitian Hamiltonians was discovered that could have a completely real eigenvalue spectrum. This special class of Hamiltonians was found to respect the property of commutation with the parity-time (PT)...
Show moreFrom the viewpoint of quantum mechanics, a system must always be Hermitian since all its corresponding eigenvalues must be real. In contrast, the eigenvalues of open systems-unrestrained because of either decay or amplification-can be in general complex. Not so long ago, a certain class of non-Hermitian Hamiltonians was discovered that could have a completely real eigenvalue spectrum. This special class of Hamiltonians was found to respect the property of commutation with the parity-time (PT) operator. Translated into optics, this implies a balance between regions exhibiting gain and loss. Traditionally, loss has been perceived as a foe in optics and something that needs to be avoided at all costs. As we will show, when used in conjunction with gain, the presence of loss can lead to a host of counterintuitive outcomes in such non-Hermitian configurations that would have been otherwise unattainable in standard arrangements. We will study PT symmetric phase transitions in various optical settings that include semiconductor microrings and coupled fiber cavities, and show how they can allow mode-selectivity in lasers. One of the key outcomes of this effort was the realization of higher order degeneracies in a three-cavity laser configuration that can exhibit orders-of-magnitude larger sensitivity to external perturbations. We will also consider systems that display nonlinear effects such as gain saturation, thus allowing novel phase transitions. Some interesting properties associated with degeneracies in non-Hermitian settings will be investigated as well. Such degeneracies, called exceptional points (EPs), are much more drastic compared to standard degeneracies of eigenvalues because the corresponding eigenvectors also coalesce, which in turn reduces the dimensionality of the phase space. We will show that dynamic parameter contours enclosing or close to EPs can lead to a robust chiral mode conversion process (-) something that can be potentially used to realize omni-polarizing optical devices.
Show less - Date Issued
- 2018
- Identifier
- CFE0007259, ucf:52182
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007259
- Title
- Time-Resolved Phosphorescence Spectroscopy at Cryogenic Temperatures for the Environmental Analysis of Polycyclic Aromatic Sulfur Heterocycles in Oil Contaminated Sites.
- Creator
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Al Tameemi, Maha, Campiglia, Andres, Zou, Shengli, Harper, James, Heider, Emily, Coffey, Kevin, University of Central Florida
- Abstract / Description
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The large volume of crude oil released into the Gulf of Mexico by the Deepwater Horizon (DWH) accident has raised considerable concerns over potential ecosystem impacts. The dispersion of harmful oil components into the ocean waters could pose long term risks to flora and fauna. Due to the complexity of oil contaminated sites, the unambiguous identification and quantitation of environmental pollutants often requires the sequence of high-performance liquid chromatography (HPLC) and gas...
Show moreThe large volume of crude oil released into the Gulf of Mexico by the Deepwater Horizon (DWH) accident has raised considerable concerns over potential ecosystem impacts. The dispersion of harmful oil components into the ocean waters could pose long term risks to flora and fauna. Due to the complexity of oil contaminated sites, the unambiguous identification and quantitation of environmental pollutants often requires the sequence of high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). A classic example is the analysis of the sixteen polycyclic aromatic hydrocarbons included in the priority pollutants list of the U.S. Environmental Protection Agency (EPA-PAHs).This dissertation tackles a different aspect of environmental analysis as is focuses on the photoluminescence spectroscopy of polycyclic aromatic sulfur heterocycles (PASHs). Since considering the EPA-PAHs alone can lead to drastic underestimations of potential toxic effects of oil spills, a strong case can be made for including hetero-aromatic compounds in risk assessments of contaminated sites. PASHs exist in an even greater variety of chemical structures than PAHs and, because of the asymmetry imposed by the heteroatom, the number of PASHs isomers is usually large. The existence of numerous isomers of the same molecular weight increases the difficulty of separation and identification by chromatographic methods.This dissertation demonstrates the capability to differentiate individual PASHs isomers of MW 234 g mol-1 via vibrational spectroscopy at liquid nitrogen (77 K) and liquid helium (4.2K) temperatures. Fluorescence and phosphorescence spectra are presented for isomer determination at the parts-per-billion (ng. mL-1) concentration levels. It is demonstrated that the relatively long phosphorescence decays of PASHs facilitate the time discrimination of strong fluorescence.interference from PAHs and methylated-PAHs often present in Normal-Phase HPLC fractions. The spectral and lifetime databases compiled in this dissertation have paved the road to explore the full dimensionality of photoluminescence spectroscopy.
Show less - Date Issued
- 2017
- Identifier
- CFE0007275, ucf:52183
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007275
- Title
- Analysis and Design of Non-Hermitian Optical Systems.
- Creator
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Kazemi Jahromi, Ali, Abouraddy, Ayman, Christodoulides, Demetrios, Likamwa, Patrick, Chini, Michael, University of Central Florida
- Abstract / Description
-
From a very general perspective, optical devices can be viewed as constructions based on the spatial engineering of the optical index of refraction. Sculpting the real part of the refractive index produces the wide variety of known passive optical devices, such as waveguides, resonators, gratings, among a plethora of other possibilities for managing the transport of light. Less attention has been directed to engineering the imaginary part of the refractive index (-) that is responsible for...
Show moreFrom a very general perspective, optical devices can be viewed as constructions based on the spatial engineering of the optical index of refraction. Sculpting the real part of the refractive index produces the wide variety of known passive optical devices, such as waveguides, resonators, gratings, among a plethora of other possibilities for managing the transport of light. Less attention has been directed to engineering the imaginary part of the refractive index (-) that is responsible for optical gain and absorption (-) in conjunction with the real part of the refractive index. Optical gain is the building block of amplifiers and lasers, while optical absorption is exploited in photovoltaic devices, photodetectors, and as dopants in lasing media. Recently, the field of non-Hermitian photonics has emerged in which the new opportunities afforded by the spatial engineering of the optical gain and loss in an optical device are being exploited. Indeed, the judicious design of such active devices can result in counterintuitive physical effects, new optical functionalities that enable unexpected applications, and enhanced performance of existing devices.In this work, we have theoretically and experimentally demonstrated four different non-Hermitian arrangements exhibiting novel non-trivial features. First, we show that the direction of energy flow can be controlled inside an active cavity by tuning the optical gain. Reversing the direction of the energy flow within the cavity (-) such that Poynting's vector points backwards towards the source (-) takes place when the cavity gain exceeds a certain threshold value, which we have named 'Poynting's threshold'. To realize this effect, we have employed a fiber-based arrangement that allows for unambiguous determining of the direction of the energy flow within the cavity. Second, we have studied the implication of Poynting's threshold with respect to spectral reflection from an active cavity. Surprisingly, the reflection at Poynting's threshold becomes spectrally flat and is guaranteed to attain unity reflectivity while maintaining non-zero transmission. In other words, at Poynting's threshold, the cavity becomes a 'transparent perfect mirror'. We have realized this effect in an on-chip active waveguide device and in an optical-fiber-based system. Third, we have examined a parity-time (PT) symmetric fiber-based cavity consisting of two coupled sub-cavities, one of which contains gain and the other loss. In contrast to all previous on-chip PT-symmetric micro-devices, the exotic features of such a system may be expected to vanish when the length of the cavity is extremely large (exceeding 1 km in our experiments) due to the strong fluctuations in the optical phase. Nevertheless, we have found that some of the central features of such a system survive; e.g., loss-induced enhancement of lasing power is still observable. Finally, we have demonstrated (-) for the first time (-) the interferometric perfect absorption of light in a weakly absorbing (erbium-doped) fiber system. Additionally, we verified that this coherent effect is the most efficient configuration with respect to utilizing the absorbing species in the medium.
Show less - Date Issued
- 2018
- Identifier
- CFE0007206, ucf:52271
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007206
- Title
- Development of a Single Sensor Approach for Capturing Three-Dimensional, Time Resolved Flame and Velocity Information.
- Creator
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Reyes, Jonathan, Ahmed, Kareem, Kassab, Alain, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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Performing non-intrusive measurements is the key to acquiring accurate information representative of what is being observed. The act of measuring often changes the environment being observed altering the information that is being obtained. Due to this, the community of fluid scientists have gravitated towards using laser-based measurements to observe the phenomena occurring in their experiments. The study of fluids has advanced since this point, utilizing techniques such as planar laser...
Show morePerforming non-intrusive measurements is the key to acquiring accurate information representative of what is being observed. The act of measuring often changes the environment being observed altering the information that is being obtained. Due to this, the community of fluid scientists have gravitated towards using laser-based measurements to observe the phenomena occurring in their experiments. The study of fluids has advanced since this point, utilizing techniques such as planar laser induced florescence (PLIF), particle image velocimetry (PIV), laser doppler velocimetry (LDV), particle doppler anemometry (PDA), etc. to acquire chemical species information and velocity information. These techniques, though, are inherently two-dimensional and cannot fully describe a flow field. In the area of reacting flow fields (combustion) acquiring the local fuel to air ratio information is increasingly important. Without it, scientist must rely on global one-dimensional metering techniques to correlate the fuel to air ratio of their flow field of interest. By knowing the fuel to air ratio locally and spatially across a flame, the location of products and reactants can be deduced, giving insight into any inefficiencies associated with a burner. Knowing the spatial fuel air field also gives insights into the density gradient associated with the flow field. Discussed in this work will be the development of a non-intrusive local fuel-air measurement technique and an expansion of the PIV technique into the third dimension, tomographic PIV, utilizing only one camera to do so for each measurement. The local fuel-air measurement is performed by recording two species (C2* and CH*) simultaneously and calibrating their ratio to the known fuel-air field. Tomographic PIV is performed by utilizing fiber coupling to acquire multiple viewpoints utilizing a single camera.
Show less - Date Issued
- 2019
- Identifier
- CFE0007523, ucf:52602
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007523
- Title
- Impact of Ionizing Radiation and Electron Injection on Carrier Transport Properties in Narrow and Wide Bandgap Semiconductors.
- Creator
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Lee, Jonathan, Flitsiyan, Elena, Chernyak, Leonid, Peale, Robert, Orlovskaya, Nina, University of Central Florida
- Abstract / Description
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This study investigated the minority carrier properties of wide and narrow bandgap semiconductors. Included specifically are wide bandgap materials GaN and ?-Ga2O3, and narrow bandgap InAs/GaSb type-II strain-layer superlattice. The importance of minority carrier behavior in bipolar device performance is utmost because it is the limiting component in current conduction. The techniques used to determine minority carrier properties include electron beam induced current (EBIC) and...
Show moreThis study investigated the minority carrier properties of wide and narrow bandgap semiconductors. Included specifically are wide bandgap materials GaN and ?-Ga2O3, and narrow bandgap InAs/GaSb type-II strain-layer superlattice. The importance of minority carrier behavior in bipolar device performance is utmost because it is the limiting component in current conduction. The techniques used to determine minority carrier properties include electron beam induced current (EBIC) and cathodoluminescence (CL) spectroscopy. The CL spectroscopy is complemented with time-resolved CL (TRCL) for direct measurement of carrier radiative recombination lifetime. The minority carrier properties and effect of high energy radiation is explored. The GaN TRCL results suggested an activation energy effecting carrier lifetime of about 90 meV which is related to nitrogen vacancies. The effects of 60Co gamma radiation are demonstrated and related to the effects of electron injection in GaN-based devices. The effects of various high energy radiations upon Si-doped ?-Ga2O3 minority carrier diffusion length and radiative lifetime are measured. The non-irradiated sample thermal activation energies found for minority carrier diffusion length were 40.9 meV, related to shallow Si-donors in the material. The CL results demonstrate that the bandgap of 4.9 eV is slightly indirect. The thermal activation energy decreased on 1.5 MeV electron irradiation but increased for 10 MeV proton irradiation. The increase in energy was related to higher order defects and their complexes, and influenced recombination lifetime significantly. Finally, the diffusion length is reported for narrow bandgap InAs/GaSb superlattice structure and the effect of 60Co gamma radiation is demonstrated.In general, the defects introduced by high energy radiations decreased minority carrier diffusion length, except for 60Co gamma on AlGaN/GaN HEMT devices and high-temperature proton irradiated ?-Ga2O3.
Show less - Date Issued
- 2018
- Identifier
- CFE0007217, ucf:52239
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007217
- Title
- Specification and Runtime Checking of Timing Constraints in Safety Critical Java.
- Creator
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Haddad, Ghaith, Leavens, Gary, Turgut, Damla, Boloni, Ladislau, Nazzal, Dima, University of Central Florida
- Abstract / Description
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The Java platform is becoming a vital tool for developing real-time and safety-critical systems. Design patterns and the availability of Java libraries, both provide solutions to many known problems. Furthermore, the object-oriented nature of Java simplifies modular development of real-time systems. However, limitations of Java as a programming language for real-time systems are a notable obstacle to producing safe real-time systems. These limitations are found in the unpredictable execution...
Show moreThe Java platform is becoming a vital tool for developing real-time and safety-critical systems. Design patterns and the availability of Java libraries, both provide solutions to many known problems. Furthermore, the object-oriented nature of Java simplifies modular development of real-time systems. However, limitations of Java as a programming language for real-time systems are a notable obstacle to producing safe real-time systems. These limitations are found in the unpredictable execution model of the language, due to Java's garbage collector, and the lack of support for non-functional specification and verification tools. In this dissertation I introduce SafeJML, a specification language for support of functional and non-functional specifications, based on an implementation of a safety-critical Java platform and the Java Modeling Language (JML). This dissertation concentrates on techniques that enable specification and dynamic checking of timing constraints for some important Java features, including methods and subtyping. SafeJML and these dynamic checking techniques allow modular specification and checking of safety-critical systems, including those that use object-orientation and design patterns. Such coding techniques could have maintenance benefits for real-time and safety-critical software.
Show less - Date Issued
- 2012
- Identifier
- CFE0004542, ucf:49224
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004542
- Title
- TEXT VERSUS VERBAL REAL-TIME FEEDBACK DURING SIMULATION-BASED TRAINING OF HIGHER-ORDER COGNITIVE SKILLS.
- Creator
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Fiorella, Christopher, Shumaker, Randall, University of Central Florida
- Abstract / Description
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A crucial component of instructional design for simulation-based training systems involves optimizing the presentation of complex material in order to maximize knowledge acquisition and application. One approach toward facilitating the learning of this complex information is to instantiate instructional strategies within the training systems themselves. However, there are few established guidelines in place which are meant specifically for real-time guidance strategies within simulation-based...
Show moreA crucial component of instructional design for simulation-based training systems involves optimizing the presentation of complex material in order to maximize knowledge acquisition and application. One approach toward facilitating the learning of this complex information is to instantiate instructional strategies within the training systems themselves. However, there are few established guidelines in place which are meant specifically for real-time guidance strategies within simulation-based environments. Consequently, this study aims to apply findings from the literature on instructional information presentation to drive decisions for how to most effectively provide real-time feedback during training of simulated decision-making tasks. Research has shown that presenting text information in an auditory mode during direct instruction of operational tasks enhances learning and reduces the probability of learners experiencing cognitive overload. Similar effects have been found regarding the presentation modality of feedback during operational tasks. In the current study, this principle was extended by comparing text versus verbal real-time feedback presentation during learning of higher-level cognitive skills in a virtual environment. Participants were instructed on how to perform a simulated decision-making task, while receiving text, verbal or no instructional feedback in real-time, based on their performance. Participants then completed an assessment scenario in which no feedback was provided to any group. It was hypothesized that a linear relationship would exist across each of the three conditions, with the verbal group making the best decisions, followed by the text group, and then by the control group. Additionally, reduced cognitive load was expected throughout the instructional process for those receiving verbal feedback prompts compared to those receiving text prompts and the control. Analyses revealed several significant linear trends across conditions regarding measures of knowledge acquisition and application. The results provide support for the hypothesis that verbal real-time feedback is more effective than text during training of primarily visual tasks for the acquisition of higher-order cognitive skills such as decision making. There were no significant linear trends regarding the amount of cognitive load subjectively reported during training and assessment. The results of this study indicate that instructional systems intended to train primarily visual tasks should present real-time feedback in verbal rather than text form.
Show less - Date Issued
- 2010
- Identifier
- CFE0003555, ucf:48915
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003555
- Title
- SPATIO-TEMPORAL ANALYSES FOR PREDICTION OF TRAFFIC FLOW, SPEED AND OCCUPANCY ON I-4.
- Creator
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Chilakamarri Venkata, Srinivasa Ravi Chandra, Al-Deek, Haitham, University of Central Florida
- Abstract / Description
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Traffic data prediction is a critical aspect of Advanced Traffic Management System (ATMS). The utility of the traffic data is in providing information on the evolution of traffic process that can be passed on to the various users (commuters, Regional Traffic Management Centers (RTMCs), Department of Transportation (DoT),
etc) for user-specific objectives. This information can be extracted from the data collected by various traffic sensors. Loop detectors collect traffic data in the form of...
Show moreTraffic data prediction is a critical aspect of Advanced Traffic Management System (ATMS). The utility of the traffic data is in providing information on the evolution of traffic process that can be passed on to the various users (commuters, Regional Traffic Management Centers (RTMCs), Department of Transportation (DoT),…etc) for user-specific objectives. This information can be extracted from the data collected by various traffic sensors. Loop detectors collect traffic data in the form of flow, occupancy, and speed throughout the nation. Freeway traffic data from I-4 loop detectors has been collected and stored in a data warehouse called the Central Florida Data Warehouse (CFDWTM) by the University of Central Florida for the periods between 1993 – 1994 and 2000 - 2003. This data is raw, in the form of time stamped 30-second aggregated data collected from about 69 stations over a 36 mile stretch on I-4 from Lake Mary in the east to Disney-World in the west. This data has to be processed to extract information that can be disseminated to various users. Usually, most statistical procedures assume that each individual data point in the sample is independent of other data points. This is not true to traffic data as they are correlated across space and time. Therefore, the concept of time sequence and the layout of data collection devices in space, introduces autocorrelations in a single variable and cross correlations across multiple variables. Significant autocorrelations prove that past values of a variable can be used to predict future values of the same variable. Furthermore, significant cross-correlations between variables prove that past values of one variable can be used to predict future values of another variable. The traditional techniques in traffic prediction use univariate time series models that account for autocorrelations but not cross-correlations. These models have neglected the cross correlations between variables that are present in freeway traffic data, due to the way the data are collected. There is a need for statistical techniques that incorporate the effect of these multivariate cross-correlations to predict future values of traffic data. The emphasis in this dissertation is on the multivariate prediction of traffic variables. Unlike traditional statistical techniques that have relied on univariate models, this dissertation explored the cross-correlation between multivariate traffic variables and variables collected across adjoining spatial locations (such as loop detector stations). The analysis in this dissertation proved that there were significant cross correlations among different traffic variables collected across very close locations at different time scales. The nature of cross-correlations showed that there was feedback among the variables, and therefore past values can be used to predict future values. Multivariate time series analysis is appropriate for modeling the effect of different variables on each other. In the past, upstream data has been accounted for in time series analysis. However, these did not account for feedback effects. Vector Auto Regressive (VAR) models are more appropriate for such data. Although VAR models have been applied to forecast economic time series models, they have not been used to model freeway data. Vector Auto Regressive models were estimated for speeds and volumes at a sample of two locations, using 5-minute data. Different specifications were fit – estimation of speeds from surrounding speeds; estimation of volumes from surrounding volumes; estimation of speeds from volumes and occupancies from the same location; estimation of speeds from volumes from surrounding locations (and vice versa). These specifications were compared to univariate models for the respective variables at three levels of data aggregation (5-minutes, 10 minutes, and 15 minutes) in this dissertation. For data aggregation levels of <15 minutes, the VAR models outperform the univariate models. At data aggregation level of 15 minutes, VAR models did not outperform univariate models. Since VAR models were used for all traffic variables reported by the loop detectors, this made the application of VAR a true multivariate procedure for dynamic prediction of the multivariate traffic variables – flow, speed and occupancy. Also, VAR models are generally deemed more complex than univariate models due to the estimation of multiple covariance matrices. However, a VAR model for k variables must be compared to k univariate models and VAR models compare well with AutoRegressive Integrated Moving Average (ARIMA) models. The added complexity helps model the effect of upstream and downstream variables on the future values of the response variable. This could be useful for ATMS situations, where the effect of traffic redistribution and redirection is not known beforehand with prediction models. The VAR models were tested against more traditional models and their performances were compared against each other under different traffic conditions. These models significantly enhance the understanding of the freeway traffic processes and phenomena as well as identifying potential knowledge relating to traffic prediction. Further refinements in the models can result in better improvements for forecasts under multiple conditions.
Show less - Date Issued
- 2009
- Identifier
- CFE0002593, ucf:48276
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002593
- Title
- CATEGORICAL PERCEPTION OF STOP CONSONANTS IN CHILDREN WITH AUTISM.
- Creator
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Bourdeau, Laura, Ryalls, Jack, University of Central Florida
- Abstract / Description
-
The purpose of this study is to determine whether children with autism recognize the same perceptual voicing boundaries of stop consonants as normally developing children of the same age group. This was explored using three groups of participants: ten children with autism between the ages of 8-14, five typically developing children between the ages of 8-14, and five typically developing seven-year-old children. Children in all groups listened to initial stop consonant syllables with voicing...
Show moreThe purpose of this study is to determine whether children with autism recognize the same perceptual voicing boundaries of stop consonants as normally developing children of the same age group. This was explored using three groups of participants: ten children with autism between the ages of 8-14, five typically developing children between the ages of 8-14, and five typically developing seven-year-old children. Children in all groups listened to initial stop consonant syllables with voicing contrasts, with voiced and voiceless cognates presented. The initial consonants were altered along a voice onset time continuum within the typically perceived boundaries of each consonant. Participants were instructed to select the box containing the letter of the initial consonant they perceive when they hear each syllable. Results revealed greater difference between the responses of the children with autism when compared with the older control group, than when compared with the younger children. The responses of the children with autism were more similar to those of the children in the second control group. This could be indicative of a delay in the children with autism of perception of the categorical boundaries along the dimension of voice onset time compared to typical children‟s perception of these consonants.
Show less - Date Issued
- 2009
- Identifier
- CFE0002796, ucf:48126
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002796
- Title
- NUMERICAL MODELING OF THE SHOCK TUBE FLOW FIELDS BEFORE ANDDURING IGNITION DELAY TIME EXPERIMENTS AT PRACTICAL CONDITIONS.
- Creator
-
lamnaouer, mouna, Kassab, Alain, University of Central Florida
- Abstract / Description
-
An axi-symmetric shock-tube model has been developed to simulate the shock-wave propagation and reflection in both non-reactive and reactive flows. Simulations were performed for the full shock-tube geometry of the high-pressure shock tube facility at Texas A&M University. Computations were carried out in the CFD solver FLUENT based on the finite volume approach and the AUSM+ flux differencing scheme. Adaptive mesh refinement (AMR) algorithm was applied to the time-dependent flow fields to...
Show moreAn axi-symmetric shock-tube model has been developed to simulate the shock-wave propagation and reflection in both non-reactive and reactive flows. Simulations were performed for the full shock-tube geometry of the high-pressure shock tube facility at Texas A&M University. Computations were carried out in the CFD solver FLUENT based on the finite volume approach and the AUSM+ flux differencing scheme. Adaptive mesh refinement (AMR) algorithm was applied to the time-dependent flow fields to accurately capture and resolve the shock and contact discontinuities as well as the very fine scales associated with the viscous and reactive effects. A conjugate heat transfer model has been incorporated which enhanced the credibility of the simulations. The multi-dimensional, time-dependent numerical simulations resolved all of the relevant scales, ranging from the size of the system to the reaction zone scale. The robustness of the numerical model and the accuracy of the simulations were assessed through validation with the analytical ideal shock-tube theory and experimental data. The numerical method is first applied to the problem of axi-symmetric inviscid flow then viscous effects are incorporated through viscous modeling. The non-idealities in the shock tube have been investigated and quantified, notably the non-ideal transient behavior in the shock tube nozzle section, heat transfer effects from the hot gas to the shock tube side walls, the reflected shock/boundary layer interactions or what is known as bifurcation, and the contact surface/bifurcation interaction resulting into driver gas contamination. The non-reactive model is shown to be capable of accurately simulating the shock and expansion wave propagations and reflections as well as the flow non-uniformities behind the reflected shock wave. Both the inviscid and the viscous non-reactive models provided a baseline for the combustion model iii which involves elementary chemical reactions and requires the coupling of the chemistry with the flow fields adding to the complexity of the problem and thereby requiring tremendous computational resources. Combustion modeling focuses on the ignition process behind the reflected shock wave in undiluted and diluted Hydrogen test gas mixtures. Accurate representation of the Shock –tube reactive flow fields is more likely to be achieved by the means of the LES model in conjunction with the EDC model. The shock-tube CFD model developed herein provides valuable information to the interpretation of the shock-tube experimental data and to the understanding of the impact the facility-dependent non-idealities can have on the ignition delay time measurements.
Show less - Date Issued
- 2010
- Identifier
- CFE0003011, ucf:48366
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003011
- Title
- STRUCTURAL HEALTH MONITORING FOR DAMAGE DETECTION USING WIRED AND WIRELESS SENSOR CLUSTERS.
- Creator
-
Terrell, Thomas, Catbas, Necati, University of Central Florida
- Abstract / Description
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Sensing and analysis of a structure for the purpose of detecting, tracking, and evaluating damage and deterioration, during both regular operation and extreme events, is referred to as Structural Health Monitoring (SHM). SHM is a multi-disciplinary field, with a complete system incorporating sensing technology, hardware, signal processing, networking, data analysis, and management for interpretation and decision making. However, many of these processes and subsequent integration into a...
Show moreSensing and analysis of a structure for the purpose of detecting, tracking, and evaluating damage and deterioration, during both regular operation and extreme events, is referred to as Structural Health Monitoring (SHM). SHM is a multi-disciplinary field, with a complete system incorporating sensing technology, hardware, signal processing, networking, data analysis, and management for interpretation and decision making. However, many of these processes and subsequent integration into a practical SHM framework are in need of development. In this study, various components of an SHM system will be investigated. A particular focus is paid to the investigation of a previously developed damage detection methodology for global condition assessment of a laboratory structure with a decking system. First, a review of some of the current SHM applications, which relate to a current UCF Structures SHM study monitoring a full-scale movable bridge, will be presented in conjunction with a summary of the critical components for that project. Studies for structural condition assessment of a 4-span bridge-type steel structure using the SHM data collected from laboratory based experiments will then be presented. For this purpose, a time series analysis method using ARX models (Auto-Regressive models with eXogeneous input) for damage detection with free response vibration data will be expanded upon using both wired and wireless acceleration data. Analysis using wireless accelerometers will implement a sensor roaming technique to maintain a dense sensor field, yet require fewer sensors. Using both data types, this ARX based time series analysis method was shown to be effective for damage detection and localization for this relatively complex laboratory structure. Finally, application of the proposed methodologies on a real-life structure will be discussed, along with conclusions and recommendations for future work.
Show less - Date Issued
- 2011
- Identifier
- CFE0003694, ucf:48837
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003694
- Title
- Les Temps Roulent: An Analysis of Emergency Medical and Police Response Times to Shootings and Lethality in New Orleans.
- Creator
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Sacra, Sarah, Corzine, Harold, Huff-Corzine, Lin, Gay, David, McCutcheon, James, University of Central Florida
- Abstract / Description
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Lethality of aggravated assaults has long been discussed in terms of weapons used, location of assault, demographics of victims, and regions of the US in which the assault occurred. However, dating back to the 1950s, medical response times have been discussed as a mediating factor, but minimally explored in analyses. The current study assesses the lethality of shootings with a primary focus on emergency medical and police response times in New Orleans, LA. Along with routine activities and...
Show moreLethality of aggravated assaults has long been discussed in terms of weapons used, location of assault, demographics of victims, and regions of the US in which the assault occurred. However, dating back to the 1950s, medical response times have been discussed as a mediating factor, but minimally explored in analyses. The current study assesses the lethality of shootings with a primary focus on emergency medical and police response times in New Orleans, LA. Along with routine activities and social disorganization indicators, 102 shootings that occurred in 3 months are analyzed to establish response time patterns of lethality. Results indicate that neither medical nor police response times impact the odds of a victim surviving a shooting, but instead, it is the days on which the violent encounters occur and the socioeconomic characteristics of the neighborhood that have a stronger influence on life or death, although not statistically significant. Limitations and future research directions are discussed.
Show less - Date Issued
- 2015
- Identifier
- CFE0005881, ucf:50877
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005881
- Title
- Community College Adjuncts: From Information Seeking to Identity Formation.
- Creator
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Hirsch - Keefe, Jennifer, Cintron Delgado, Rosa, Owens, J. Thomas, Bosley, Michael, Biraimah, Karen, University of Central Florida
- Abstract / Description
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This phenomenological study addressed the transitions of biology and chemistry adjunct faculty, with full or part-time positions outside of academia, as they navigate the transition between their workplaces and the academic environment and also transition toward becoming confident and competent educators. Using the final two stages of Schoening's (2013) Nurse Educator Transition (NET) Model as a framework, this qualitative study examines the transitions of nine biology and chemistry adjuncts...
Show moreThis phenomenological study addressed the transitions of biology and chemistry adjunct faculty, with full or part-time positions outside of academia, as they navigate the transition between their workplaces and the academic environment and also transition toward becoming confident and competent educators. Using the final two stages of Schoening's (2013) Nurse Educator Transition (NET) Model as a framework, this qualitative study examines the transitions of nine biology and chemistry adjuncts at College Alpha, which is a community college located in a southern state. Study findings indicated both degrees of transition, the day-to-day and the overall transition into teaching, impact the overall adjunct experience. The College's involvement with the adjunct and the generational differences between the adjuncts and their students also play a role in the transitions. The literature review addressed the use of the NET Model as a means of examining transitions toward teaching, the roles of adjunct faculty on college campuses, the workplace transition, and the particular needs of Millennial students are also addressed. The study culminated with conclusions about the experiences of the participants, recommendations for future research, and calls for action by community colleges to improve the adjunct experience. A chapter is also included that reflects upon the dissertation writing experience and the challenges of qualitative research not addressed in graduate programs.
Show less - Date Issued
- 2015
- Identifier
- CFE0005955, ucf:50801
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005955
- Title
- Estimating a Freight Mode Choice Model: A Case Study of Commodity Flow Survey 2012.
- Creator
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Keya, Nowreen, Eluru, Naveen, Abdel-Aty, Mohamed, Radwan, Essam, University of Central Florida
- Abstract / Description
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This research effort develops a national freight mode choice model employing data from the 2012 Commodity Flow Survey (CFS). While several research efforts have developed mode choice model with multiple modes in the passenger travel context, the literature is sparse in the freight context. The primary reasons being unavailability and/or the high cost associated with the acquisition of mode choice and level of service (LOS) measures (-) such as travel time and travel cost. The first...
Show moreThis research effort develops a national freight mode choice model employing data from the 2012 Commodity Flow Survey (CFS). While several research efforts have developed mode choice model with multiple modes in the passenger travel context, the literature is sparse in the freight context. The primary reasons being unavailability and/or the high cost associated with the acquisition of mode choice and level of service (LOS) measures (-) such as travel time and travel cost. The first contribution of the research effort is to develop travel time and cost measures for various modes reported in the CFS. The study considers five modes: hire truck, private truck, air, parcel service and other modes (rail, ship, pipeline, and other miscellaneous single and multiple modes). The LOS estimation is undertaken for a sample of CFS 2012 data that is partitioned into estimation sample and holdout sample. Subsequently, a mixed multinomial logit model is developed using the estimation sample. The exogenous variables considered in the model include LOS measures, freight characteristics, and transportation network and Origin-Destination variables. The model also accounts for unobserved factors that influence the mode choice process. The estimated mode choice model is validated using the holdout sample. Finally, a policy sensitivity analysis is conducted to illustrate the applicability of the proposed model.
Show less - Date Issued
- 2016
- Identifier
- CFE0006835, ucf:51766
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006835
- Title
- Modeling Learner Mood in Realtime through Biosensors for Intelligent Tutoring Improvements.
- Creator
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Brawner, Keith, Gonzalez, Avelino, Boloni, Ladislau, Georgiopoulos, Michael, Proctor, Michael, Beidel, Deborah, University of Central Florida
- Abstract / Description
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Computer-based instructors, just like their human counterparts, should monitor the emotional and cognitive states of their students in order to adapt instructional technique. Doing so requires a model of student state to be available at run time, but this has historically been difficult. Because people are different, generalized models have not been able to be validated. As a person's cognitive and affective state vary over time of day and seasonally, individualized models have had differing...
Show moreComputer-based instructors, just like their human counterparts, should monitor the emotional and cognitive states of their students in order to adapt instructional technique. Doing so requires a model of student state to be available at run time, but this has historically been difficult. Because people are different, generalized models have not been able to be validated. As a person's cognitive and affective state vary over time of day and seasonally, individualized models have had differing difficulties. The simultaneous creation and execution of an individualized model, in real time, represents the last option for modeling such cognitive and affective states. This dissertation presents and evaluates four differing techniques for the creation of cognitive and affective models that are created on-line and in real time for each individual user as alternatives to generalized models. Each of these techniques involves making predictions and modifications to the model in real time, addressing the real time datastream problems of infinite length, detection of new concepts, and responding to how concepts change over time. Additionally, with the knowledge that a user is physically present, this work investigates the contribution that the occasional direct user query can add to the overall quality of such models. The research described in this dissertation finds that the creation of a reasonable quality affective model is possible with an infinitesimal amount of time and without (")ground truth(") knowledge of the user, which is shown across three different emotional states. Creation of a cognitive model in the same fashion, however, was not possible via direct AI modeling, even with all of the (")ground truth(") information available, which is shown across four different cognitive states.
Show less - Date Issued
- 2013
- Identifier
- CFE0004822, ucf:49734
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004822
- Title
- A Time-Course Analysis of Behavioral Plasticity and Differential Gene Expression Patterns in Response to Density in Schistocerca americana (Orthoptera: Acrididae).
- Creator
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Gotham, Steven, Song, Hojun, Vonkalm, Laurence, Fedorka, Kenneth, University of Central Florida
- Abstract / Description
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Phenotypic plasticity is the ability of the genotype to express alternative phenotypes in response to different environmental conditions and this is considered to be an adaptation in which a species can survive and persist in a rapidly changing environment. Some grasshoppers and locusts are capable of expressing an extreme form of density-dependent phenotypic plasticity, known as locust phase polyphenism. At low population density, the individuals typically have a cryptic coloration as nymphs...
Show morePhenotypic plasticity is the ability of the genotype to express alternative phenotypes in response to different environmental conditions and this is considered to be an adaptation in which a species can survive and persist in a rapidly changing environment. Some grasshoppers and locusts are capable of expressing an extreme form of density-dependent phenotypic plasticity, known as locust phase polyphenism. At low population density, the individuals typically have a cryptic coloration as nymphs, are less active, and only seek out conspecifics for reproductive purposes. At high density, however, they develop a drastically different phenotype in which they have a conspicuous coloration, are much more active, and tend to stay together in large groups. The American Birdwing grasshopper, Schistocerca americana, is a non-swarming species related to the desert locust, S. gregaria, which shows density-dependent phenotypic plasticity in behavior, color, and morphology. In this thesis, I have identified the duration of crowding necessary for a 6th instar S. americana reared in the isolated condition to express the typical crowded behavior. The behavior changed after just one hour of crowding and the effect of crowding diminished after 48 hours to near-complete isolated behavior. In reverse, the crowded condition was isolated, but behavior did not significantly change over time. Gene expression of the following three genes suspected of having a role in behavior change were investigated based on studies of S. gregaria: protein kinase A (PKA), L-Tryptophan-5-monooxygenase (T-5), and Aromatic L-amino acid decarboxylase (Decarb). T-5 was up-regulated in the long-term isolated condition compared to the long-term crowded condition. T-5 and Decarb were up-regulated in isolated individuals that were crowded for 10 hours compared to the long-term isolated condition. This study represents a novel contribution in the study of phenotypic plasticity as it establishes the time course of behavioral and molecular plasticity in a non-swarming grasshopper for the first time.
Show less - Date Issued
- 2014
- Identifier
- CFE0005799, ucf:50049
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005799
- Title
- Scene Understanding for Real Time Processing of Queries over Big Data Streaming Video.
- Creator
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Aved, Alexander, Hua, Kien, Foroosh, Hassan, Zou, Changchun, Ni, Liqiang, University of Central Florida
- Abstract / Description
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With heightened security concerns across the globe and the increasing need to monitor, preserve and protect infrastructure and public spaces to ensure proper operation, quality assurance and safety, numerous video cameras have been deployed. Accordingly, they also need to be monitored effectively and efficiently. However, relying on human operators to constantly monitor all the video streams is not scalable or cost effective. Humans can become subjective, fatigued, even exhibit bias and it is...
Show moreWith heightened security concerns across the globe and the increasing need to monitor, preserve and protect infrastructure and public spaces to ensure proper operation, quality assurance and safety, numerous video cameras have been deployed. Accordingly, they also need to be monitored effectively and efficiently. However, relying on human operators to constantly monitor all the video streams is not scalable or cost effective. Humans can become subjective, fatigued, even exhibit bias and it is difficult to maintain high levels of vigilance when capturing, searching and recognizing events that occur infrequently or in isolation.These limitations are addressed in the Live Video Database Management System (LVDBMS), a framework for managing and processing live motion imagery data. It enables rapid development of video surveillance software much like traditional database applications are developed today. Such developed video stream processing applications and ad hoc queries are able to "reuse" advanced image processing techniques that have been developed. This results in lower software development and maintenance costs. Furthermore, the LVDBMS can be intensively tested to ensure consistent quality across all associated video database applications. Its intrinsic privacy framework facilitates a formalized approach to the specification and enforcement of verifiable privacy policies. This is an important step towards enabling a general privacy certification for video surveillance systems by leveraging a standardized privacy specification language.With the potential to impact many important fields ranging from security and assembly line monitoring to wildlife studies and the environment, the broader impact of this work is clear. The privacy framework protects the general public from abusive use of surveillance technology; success in addressing the (")trust(") issue will enable many new surveillance-related applications. Although this research focuses on video surveillance, the proposed framework has the potential to support many video-based analytical applications.
Show less - Date Issued
- 2013
- Identifier
- CFE0004648, ucf:49900
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004648
- Title
- Expressing Future Time in Spoken Conversational English: A Corpus-Based Analysis of the Sitcom Friends.
- Creator
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Harris, Brandon, Folse, Keith, Mihai, Florin, Vitanova-Haralampiev, Gergana, University of Central Florida
- Abstract / Description
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Far from being simply will, a survey of English grammar textbooks revealed that a multitude of expressions exists in the English language to express the future time. These expressions include, but are not limited to, will, be going to, the simple present tense, modals, the future perfect tense, and the present progressive tense. With so many choices and with a lack of direct relationship between tense and time, a language learner may certainly have difficulties in choosing which expression to...
Show moreFar from being simply will, a survey of English grammar textbooks revealed that a multitude of expressions exists in the English language to express the future time. These expressions include, but are not limited to, will, be going to, the simple present tense, modals, the future perfect tense, and the present progressive tense. With so many choices and with a lack of direct relationship between tense and time, a language learner may certainly have difficulties in choosing which expression to use when attempting to produce a future utterance. A corpus-based approach to analyzing real language has been demonstrated to be quite useful for the field of TESOL (Biber, Conrad, (&) Reppen, 1996; Biber (&) Conrad, 2001; Biber (&) Reppen, 2002) and numerous studies on the frequency of lexical and grammatical items of language have revealed salient features that otherwise would have remained unknown. Adding to this body of knowledge, the current study was an analysis of future expressions in spoken conversational English using the television sitcom Friends as a corpus. A careful analysis of 349,106 words from transcripts of 117 randomly selected episodes revealed that the most common expression of the future in the English language is the contracted form of be going to (-) gonna. The results of the study also revealed that only six future expressions emerged in this spoken conversational English from this corpus: will, be going to, the simple present tense, the present progressive tense, modals, and be about to.
Show less - Date Issued
- 2013
- Identifier
- CFE0004860, ucf:49695
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004860
